Smashing process of permanent ferrite pre-sintering material

Abstract

The invention discloses a smashing process of permanent ferrite pre-sintering material, belonging to the field of permanent ferrite. The smashing process is divided into two stages; in a first stage, rotating speed of a ball grinding mill is 26-35 turns per minute, grinding time in the first stage is 6-9 hours; in a second stage, the rotating speed of the ball grinding mill is 19-22 turns per minute, the grinding time in the second stage is 7-10 hours, ribs on the two end covers of a barrel of the ball grinding mill are raised upward in arc shape, two ball grinding mills are adopted preferably, mass ratio of material powder to ball to water is controlled to be 1: (4-6): (1.2-1.6) in the first stage, and the mass ratio of the material powder to the ball to the water is controlled to be 1: (4-6): (1.4-1.8). By adopting the smashing process disclosed by the invention, the grinding time is shortened by 20-35%, green blank moulding period is shortened by 8.8-21%, green blank density is improved by 1.9-3.6%, Br of a product is improved by 5mT(50Gs) to 20mT(200Gs), Hcj of the product is improved by 7kA / m(88Oe) to 14kA / m(176Oe), squareness ratio is improved by 3-5%, and comprehensive qualified rate of the product is improved by more than 10%.

Description

technical field [0001] The invention relates to a production method of permanent magnet ferrite, in particular to a crushing process of permanent magnet ferrite calcined material. Background technique [0002] In the production and preparation process of permanent ferrite, the pre-fired blank is a porous, defective, low-density partial ferrite material, its grain size and distribution are not uniform, and the solid-state reaction is not complete. The main function of fine crushing is to crush and grind the calcined material so as to obtain the particle size required for molding and the chemical reaction contact surface required for sintering, and promote the densification of the product and the growth of grains. [0003] If the particle size distribution after fine pulverization is too large, it is easy to cause obvious discontinuous grain growth, thereby deteriorating the magnetic properties of ferrite. The narrower the particle size distribution, that is, the more uniform ...

AI Technical Summary

Problems solved by technology

Adopting the ball mill method of uniform rotation, the particle size distribution of the permanent magnet ferrite slurry is uneven, and the degree of orientation of the magnet is reduced. After the slurry is formed and sintered, the crystal size is uneven, the product density is poor, and the magnetic properties are difficult to improve.

[0015] Xu Wensheng and others mentioned in the article "New Developments in Permanent Ferrite Technology" (Magnetic Materials and Devices, 2004, 35: 36-39) that graded grinding can significantly improve the particle size distribution of the slurry, but the The impact of the number of stages, different rotation speeds in different stages, and the viscosity of the slurry on the grinding effect has not been mentioned.

[0016] The patent application number is CN200910216165.1, which proposes a grinding method including multi-stages and different rotating speeds. Compared with the existing technology, it has a certain improvement and can improve the magnetic performance to a certain extent, but it also has the following disadvantages: one is , the total grinding time is longer, 22 to 27 hours, which makes its production efficiency lower; second, the steel balls used are mixed steel balls of φ3 to 8, and the diameters of the steel balls vary greatly. The amount of steel balls of each size is not clear. In fact, there is a close relationship between the diameter of the steel ball and the particle size of the feed. The smaller the diameter of the ball, the reasonable control of the diameter of the steel ball will also greatly improve the performance of the permanent magnet ferrite. This patent application does not disclose the relevant control parameters; the third is that at each stage During the grinding and crushing process, due to the relatively fixed ratio of "material powder: steel ball: water", the unreasonable control of the rotational speed, and the need for improvement in the structure of the ball mill, the magnetic properties of the obtained magnets still have room for improvement. Space; Fourth, the process parameters mentioned in this patent are not suitable for large-scale production (the first stage, 50-80 rpm, the second stage, 30-60 rpm, the third stage, 20-50 rpm ), if the rotation speed of the roller ball mill used for large-scale production exceeds 35 rpm, you will not hear the intermittent "唰—唰——" sound of the steel ball being thrown up and smashing the steel ball, that is, the steel ball The ball will run in the manner shown in Figure 2.(c), and the grinding and crushing effects are poor. Fifth, in practice, the rotation speed of the ball mill is related to factors such as the size of the steel ball, the friction effect, the state of the material, and the diameter of the cylinder of the ball mill. , but the patent does not explicitly mention

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